Organo-disiloxane and methods of preparing it



Patented Oct. 19, 1948 ORGANO-DISILOXANE, AND METHODS OF PREPARING rr William Herbert Daudt, Corning, N. Y., assignor to Corning Glass Works, Corning, N. Y., a corporation of New York No Drawing. Application August 9, 1945,

. Serial No. 609,919 g 1 This invention relates to a new and useful composition of matter and its preparation, and, more particularly, to an organo-disiloxane and methods of making it.

The present application is a continuation-inpart of my copending application, Serial Number 481,152, filed March 30, 1943, and assigned to the assignee of the present invention.

For many hydraulic and damping applications I it' would be desirable to have as the hydraulic 1 Claim. (Cl. 260-4482) 2 (B. P. 295 C./760 mm.) and bis-trimethylsilicyl 'oxide (also known as hexamethyldisiloxane) or damping medium a liquid which possesses high thermal stability; resistance to oxidationat high temperatures; little change of viscosity with temperature; low pour point; high flash point; low volatility; low hydroscopicity; little or no corrosion or decomposing effect upon metal or rubber; and little or no gasiflcation or solidification tendencies under the higher or lower temperature conditions encountered in various types of applications. Most liquids actually used in such applications represent a compromise so far as the above properties are concerned.

The primary object of the present invention is to provide a liquid which possesses properties rendering it especially adapted for use as a hydraulic or damping medium over a temperature .range of -75 C. to at least 200 C. Other objects and advantages will become apparent from the following description and claim.

I have discovered a liquid composition which possesses to a remarkable extent the desirable properties listed above. This liquid is pentamethylphenyldisiloxane having the structural formula C H: C H;

C oHs-Si-O- i-C HI C Hi Hi It boils at 206 C. at atmospheric pressure (760 mm.) and has a melting point below -80 0. Its viscosity at C. is 1.3 centistokes. Compared to conventional hydraulic oils of the hydrocarbon type it exhibits relatively little change in viscosity preparing the compound of my invention.

Example 1 Bls-phenyldimethylsilicyl oxide (al o known as symmetrical tetramethyldiphenyldisiloxane) (B. P. 98.5 C./760 mm.) were saturated with dry hydrogen chloride and then allowed to stand for one day. After washing with water the solution was distilled. The distillation curve showed the presence of a small amount of a new compound which possessed a boiling point intermediate between those of the starting materials. To this mixture was added approximately three times its volume of anhydrous ethyl ether and a small amount of calcium chloride. When the dry ether solution was saturated with dry hydrogen chloride a considerably larger quantity of the gas was dissolved. After standing three days the solution was washed with water. and then distilled. On distillation there was then obtained a large proportion of the new compound which was shown by analysis to be pentamethylpheny'ldisiloxane, also known as phenyldimethylsilicyl trimethylsllicyl oxide (B. P. 206 C./760 mm.).

Example 2 Pentamethylphenyldisiloxane may also be obtained from a mixture of ethoxydimethylphenylsilane and ethoxytrimethylsilane in substantially equimolar proportions by hydrolyzing the mixture with aqueous hydrochloric acid, washing and distilling the reaction mixture. If desired, a mixture of the corresponding chlorosilanes may be employed instead of the ethoxysilanes and simiv lar results will be obtained.

Example 3 To 1.00 g. (0.010 mole) of 96% sulfuric. acid was added slowly 81.16 g. (0.500 mole) of hexamethyldisiloxane in small portions. Most of the disiloxane remained in a. separate phase, even when it was warmed to C. Next, an equal molecular quantity (143.23 g.) of sym.-tetramethyldiphenyldisiloxane was added to the mixture at room temperature. The mixture was stirred vigorously for a week. After the dark acid drops had settled the silo'xane phase was clear and colorless. Following decanting and rinsing with several milliliters of hexamethyldlsiloxane, the siloxanes were treated with excess gaseous ammonia. Ammonium sulfate precipitated slowly. was filtered and rinsed with hexamethyldisiloxane after standing overnight. The

slightly ammoniacal filtrate was fractionally distilled through a 2 /2 ft. column containing V4 in. glass helices and through a Corad head using a 1:5 reflux ratio. I

Inspection of the distillation data showed that vylphenyl- 3 the mixed disiloxane (CsHsHCHaMSiOSMCHa): was a major product and was shown by analysis to be present in a pure state in the fraction'boiling between 108 and 110 C. at 29 mm. The presence of triand tetra-siloxanes formed by cleavage of some of the phenyl groups in certain of the distillate fractions was also established. Such compounds contained dimethylsiloxane units and were higher boiling and of higher sili-- con content than the disiloxanes containing the same number of phenyl groups. These by-products probably included octamethyi-, heptamethand hexamethyldiphenyltrisiloxanes, formed by combined dephenylation and redistribution. For example a. fraction boiling between 116 and 119 C. at 12 mm. was shown by analysis to be essentially (CBHs) (CH3) 2Si-O-SKCH3) 2-0-Si(CH3) 3 Example 4 A mixture of 7.2 g. of bis-phenyldimethylsilicyl oxide and 20.3 g. of bis-trimethylsilicyl oxide was allowed'to stand 24 hours at room temperature with 1 g. of potassium hydroxide dissolved in 23 g. of 95% ethanol. The solution was then washed with water. Distillation gave some of the start- -ing dimeric silicon compounds and, in addition,

a compound which possessed an intermediate boiling point of 206 C. at 760 mm Analysis established it to be the unsymmetrical oxide, pentamethylphenyldisiloxane.

p In view of the wide range of temperatures, namely, .80 C. to 206 C. over which the disiloxane of this invention remains substantially un- 4 changed, it is eminently adapted for use as a damping fluid for vibrating members or as a hydraulic fluid for fluid pressure actuatable devices.

However, other uses than those of hydraulic ap-' plications exist for which such a composition is urgently needed. These are thermoresponsive fluids, heat transfer liquids and constant temperature media.

I claim: Pentamethylphenyldisiloxane.

-r 1| HERBERT DAUDT.

REFERENCES CIT The following references are of record in the file of this patent:

vol. (1927) pages 109-107.-

II. Kipping Journal Chem. Soc." (London) vol. 99 (1911) pages 138-145. III. Kipping "Journal Chem. Soc." (London) vol. 93 (1908) P es 198-210. 

